The computer may show only 64MB of memory being used at the moment but that is because the computer is not under load, if for example you started playing a game the system would automatically allocate the amount of memory required, how much will be allocated will be determined by the amount of physical Ram available and the OS, for Windows 7 64-bit a maximum of circa 1760MB, see below;
3rd Generation Intel®
with Intel® HD
(Paired with Intel® 7
Series Chipsets) Windows 2000 = Unsupported XP operating system = Up to 1 GB Vista = Unsupported operating system Windows 7 = Up to ~1.7GB
Can I control how much graphics memory is used by a single application?
The Intel® Graphics Driver Properties window does not have a user-configurable setting to control or increase the amount of graphics memory used by a single application. The amount of graphics memory in use is dynamically allocated to balance the needs of the operating system and all running applications.
Have you checked the HW Set Up area in the BIOS to see if there are any other display tweaks that can be made, user manual here